drawtext limitation in number of opened font files

Description

If you build simple filtergraph with drawtext filters you will notice it has a limitation of setmaxstdio in number of drawtext filters you can apply at once on Windows. It is connected with C-runtime limitation of max number of opened files. Although I use all the time the same font each time new drawtext filter is parsed, the same font is opened once again. Maybe it is possible to introduce some global storage for current/recent fonts? Then instead of opening once again the same font it would be possible to reuse it? Function _setmaxstdio can be investigated, as it is partially connected with this problem.

Hi. It's reproducible for me for filter_complex. It works only with about 512 drawtext filters after that ffmpeg writes that it cannot find default "Sans" font. So looks like problem with filter_complex is still exists and setmaxstdio is still set as the max font files for drawtext.